1. The Field of the Invention
The present invention relates generally to implanting medical devices within a patient. More particularly, the present invention relates to the field of patent foramen ovale (“PFO”) closure devices.
2. The Relevant Technology
FIGS. 1A-1C depict various views of a heart. Heart 10 is shown in a cross-section view in FIG. 1A. In a normal heart, the right atrium 30 receives systemic venous blood from the superior vena cava 15 and the inferior vena cava 25 and then delivers the blood via the tricuspid valve 35 to the right ventricle 60. However, in heart 10, there is a septal defect between right atrium 30 and left atrium 40 of a patient's heart which is referred to as a patent foramen ovale (“PFO”). PFO is a birth defect that occurs when an opening between the upper two chambers of the heart fail to close after birth to a lesser or greater degree. This birth defect is sometimes also known as a “hole in the heart.”
Other problems with this condition are that a blood clot may travel freely between the left or right atria of the heart, and end up on the arterial side. This could allow the clot to travel to the brain, or other organs, and cause embolization, or even a heart attack. These and other similar defects (septal or otherwise), where some tissue needs to be closed to function properly include the general categories of atrial septal defects (“ASDs”), ventricular septal defects (“VSCs”) and patent ductus arterosus (“PDA”), and so forth.
The PFO, which is an open flap on the septum between the heart's right and left atria, is generally identified at 50. In a normal heart, left atrium 40 receives oxygenated blood from the lungs via pulmonary arteries 75 and then delivers the blood to the left ventricle 80 via the bicuspid valve 45. However, in heart 10 some systemic venous blood also passes from right atrium 30 through PFO 50, mixes with the oxygenated blood in left atrium 40 and then is routed to the body from left ventricle 80 via aorta 85.
During fetal development of the heart, the interventricular septum 70 divides right ventricle 60 and left ventricle 80. In contrast, the atrium is only partially partitioned into right and left chambers during normal fetal development as there is a foramen ovale. When the septum primum 52 incompletely fuses with the septum secundum 54 of the atrial wall, the result is a PFO, such as the PFO 50 shown in FIGS. 1A-1C, or an atrial septal defect referred to as an ASD.
FIG. 1C provides a view of the crescent-shaped, overhanging configuration of the typical septum secundum 54 from within right atrium 30. Septum secundum 54 is defined by its inferior aspect 55, corresponding with the solid line in FIG. 1C, and its superior aspect 53, which is its attachment location to septum primum 52 as represented by the phantom line. Septum secundum 54 and septum primum 52 blend together at the ends of septum secundum 54; these anterior and posterior ends are referred to herein as “merger points” and are respectively identified at 56a and 56p. The length of the overhang of septum secundum 54, the distance between superior aspect 53 and inferior aspect 55, increases towards the center portion of the septum secundum 54 as shown.
A tunnel 58 is defined by portions of septum primum 52 and septum secundum 54 between the merger points 56a and 56p which have failed to fuse. The tunnel 58 is often at the apex of the septum secundum 54 as shown. When viewed within right atrium 30, the portion of septum secundum 54 to the left of tunnel 58, which is referred to herein as the posterior portion 57p of the septum secundum 54, is longer than the portion of the septum secundum 54 to the right of tunnel 58, which is referred to herein as the anterior portion 57a of the septum secundum 54. In addition to being typically longer, the left portion also typically has a more gradual taper than the right portion, as shown. The area defined by the overhang of the anterior portion 57a of septum secundum 54 and the septum primum 52 and extending from the anterior merger point 56a toward tunnel 58 is an anterior pocket 59a. Similarly, the area defined by the overhang of the posterior portion 57p of septum secundum 54 and the septum primum 52 and extending from the posterior merger point 56p toward tunnel 58 is a posterior pocket 59p. 
Conventional treatments for PFO (and related conditions), have generally involved invasive surgery, which presents a different, new set of risks to a patient. Although there are some less invasive treatments for PFO, these have typically been less efficient at closing the PFO opening than techniques involving invasive surgery. Accordingly, there is a continuing need for improved methods and devices for closing the PFO opening. In particular, there is a need for improved methods and devices for deploying PFO closure anchors in a patient.